how to extract method from iqueryable and apply to new context

I have a subclassed ListBox with the following property:

Property Query As Func(Of IEnumerable)

this i use all over like this

MyListBox.Query=Function() MyDBContext.Products

or

MyListBox.Query=Function() MyDBContext.Clients.Where(function(x) x.Age>25)

etc

I now see that the way I use the Query property all over, never disposes of the MyDBContext, since I'm not using Using

so the question is:

Is there a way in my ListBox to grab only the function part of the func (i.e. .Clients.Where(function(x) x.Age>25) and apply it to a different dbcontext that i will use and dispose of internally in MyListBox?

Thank you very much